This invention relates to apparatus for high speed centrifuging and, more specifically, to centrifuge tubes which are particularly useful for obtaining analytical samples.
In the field of high speed centrifugation, it is frequently desired to draw off a sample of a sedimentation specimen from a centrifuge test tube. Since the sedimentation layer of interest lies at a specific level in the tube, it is necessary to capture the sample without causing it to become remixed with an adjacent layer. A Pasteur pipette or hypodermic needle and syringe can be used to draw off the desired fraction through the mouth of the tube. If the particles are of a size which can be detected visually, it is most desirable for the centrifuge test tube to be transparent so as to enable visual identification of the desired fraction. It is known that extraction of a heavy sedimentation fraction can be made with some advantage from the bottom of a centrifuge tube because the heaviest particles lie closest to the tube bottom. To do this, a syringe having a hypodermic needle is utilized in conjunction with a test tube having a penetrable bottom. A centrifuge tube of this type is disclosed by Kjetil Gauslaa in U.S. Pat. No. 3,081,029 entitled "Improved Centrifuge Tube", issued Mar. 12, 1963. The Gauslaa tube, however, has several drawbacks. One disadvantage, for example, is that the tube which is made of metal, is not transparent and, thus, the user cannot view the sedimentation pattern, nor can he visually monitor his effort to extract the fraction of his choosing. Another drawback of this metal construction is that it makes the tube heavier than tubes made of plastic. The greater tube weight may require that the centrifuge rotor be restricted to a lower speed range to prevent its being overstressed, with the result that longer centrifugation cycles may be necessitated. Finally, the Gauslaa tube is obviously complex and relatively expensive to manufacture.
Another centrifuge tube having a penetrable bottom is disclosed by Gordon L. Dorn et al. in U.S. Pat. No. 3,875,012 entitled "Apparatus and Method for the Detection of Microbial Pathogens", issued Apr. 1, 1975. The Dorn tube is essentially a right circular cylinder closed by a resilient stopper at each end. Although it is possibly capable of withstanding somewhat more, the Dorn tube is specified for use only up to 6,000 G's. It may be seen by inspection that the design of the Dorn tube is unsuited to withstand forces in the range of 150,000 gravities without leaking. This is evident by the disposition of the straight sided tube which is employed, and which would be subject to expansive deformation and resultant leakage under extreme load.
Accordingly, there has been shown to be a need for a puncturable-bottom centrifuge tube which is transparent and which can withstand forces in the region of 150,000 G's.